Like most journalists with broadly defined beats, my personal bias shows up in the coverage choices that I make. So, even though I know pretty much any storage about electric vehicles that decide to post here will drive a gratifying increase in readership, my green-tech interests in the waning days of 2011 are focused on other fundamental matters. In particular, I've been thinking a lot about which developments in green water technology I should be following during the next 12 months.

After sifting through a number of resources, I've come up with this list of start-up or early stage companies that I'll be watching as closely as possible. All of the companies on this particular to-watch list are focused on technologies for treating wasterwater, and all of them have been part of various cleantech innovation competitions this fall. I've organized the list alphabetically and offered my brief rationale for planning to watch each company.

APTWater (Long Beach, Calif.): Treats wastewater with an eye toward enabling reuse. The company merged with Europe's Rochem in November 2011 and boasts several municipal deals on its Web site.

aquaMost (Madison, Wis.): Uses ultraviolet light and patented catalysts to purify water. In late November 2011, the company snagged $3 million in a second round of venture capital; it was also awarded a $1 million phase II Small Business Innovation Research grant by the National Institutes of Health.

Aqwise (Israel): Develops biofilm technologies to remove nutrients, carbon and other substances. Has municipal pilot history in the United States and Spain.

Arbsource (Tempe, Ariz.): Makes a reactor system designed to be used by food and manufacturing companies.

Emefcy (Israel): Creates energy-efficient water treatment technology by using sewage-eating bacteria. In August 2011, the company snagged about $10 million in venture funding from GE, NRG Energy and ConocoPhillips.

Fogbusters (Oakland, Calif.): Takes the FOG (fats, oil, grease) out of wastewater. Customers included Cadbury and United Biscuits.

Nexus eWater (Australia): Bills itself as maker of technology that can recycle graywater to a near potable condition, while also offering an alternative for reducing hot water energy costs. The company snagged two Australian grants in August 2011.

Ostara Nutrient Recovery Technologies (Vancouver): Removes nutrients from wastewater and converts that into fertilizer than can be used by a revenue source. The venture capital-backed company has three recovery facilities in the United States and recently authorized one for Saskatoon, Canada.